Kleinbrook Animal Hospital

(281) 444-8387




Dogs and cats can become hosts to many intestinal parasites and a few general statements apply to all parasitic infections:

  • All deworming medicines are poisonous to some extent and should only be used as needed and under proper conditions.
  • At this time there is no one dewormer that can eliminate all species of parasites.  Consequently an accurate diagnosis is necessary to treat your pet properly.
  • Diagnosis is usually made from a fresh stool sample (passed less than 12 hours) or, in the case of tapeworms, seeing the segments in the stool.
  • Most puppies and kittens are infected before birth and, for this reason, will need deworming starting at 6 weeks of age. If hookworms are suspected, stools should be checked starting as early as 2-3 weeks. 
  • Occasionally, for a heavy parasitic infection, 3 or even 4 treatments may be necessary to eliminate the parasite.


How do these worms infect people?


Dogs and cats infected with these worms contaminate their surroundings by passing eggs or larvae in their feces (bowel movement). Because pets will pass feces anywhere, they may contaminate a large area quickly. These eggs and larvae are resilient and can survive in areas such as parks, playgrounds and yards. Even inside houses.


People get roundworms and hookworms infections through direct contact with infected feces. This usually happens by chance ingestion of contaminated soil, sand or plant life.


Hookworm larvae penetrate the skin. Children are more vulnerable to infection than adults, perhaps because they play on the ground with dirt that may be contaminated. Maybe it’s because kids are more likely to put dirty objects into their mouths. They also let dogs lick them. Some children pass through a stage in which they eat dirt (pica). Thus they are more prone to get these infections.



This is a common worm of puppies and kittens, but can be seen in any age dog or cat. Diagnosis is made from a microscopic examination of the feces. Treatment is an oral medication given in several doses. Symptoms will vary from none to marked vomiting and diarrhea, and abdominal swelling.


Transmission to adult dogs and cats occurs by infected feces contaminating the yard. As a result, prevention is accomplished by isolating your pet from infected feces of other animals. For dogs, the heartworm preventives also prevent roundworm infection.


Transmission to humans is rare. Roundworms enter the body when ingested as eggs that soon hatch into larvae. These larvae travel through the liver, lungs and other organs. In most cases, these “wandering worms” cause no symptoms or apparent damage. However, in some cases they produce a condition known as “visceral larval migrans.” The larvae may cause damage to the tissue and sometimes affect the nerves or even lodge in the eye. In some cases, they may cause permanent nerve or eye damage, even blindness.



This is also a common worm of puppies and kittens but is seen with equal frequency in adults. This parasite sucks your pet’s blood and can cause severe anemia. Diagnosis is made from a microscopic examination of your pet’s stool. Treatment is an oral medication given in several doses.  Symptoms will vary from none to blood in the stool (dark tar-colored stool) with diarrhea. Severe cases may need a transfusion and hospitalization.  Transmission to adults occurs by infected feces contaminating the grass or soil. Prevention, therefore, requires that the pet be kept away from contaminated areas. Heartworm preventive can also prevent hookworm infections in dogs.


Transmission to humans is uncommon. Hookworm larvae typically move about within the skin, causing inflammation in the affected skin. This is called cutaneous (skin) larva migrans. One type of hookworm can penetrate into deeper tissues and cause more serious damage to the intestines and other organs.                                     



This worm affects dogs only. Diagnosis is also made from a microscopic exam of the feces. Eggs from this parasite pass intermittently, however, so it may be necessary to check multiple fecals before a diagnosis is made. Treatment is an oral medication given for several treatments depending on the severity of the infection.  Symptoms vary from none to a severe watery diarrhea, vomiting, and marked weight loss. Some dogs require hospitalization for treatment of dehydration, malnutrition, and infection. There is no human transmission.



This common worm affects both dogs and cats. Transmission occurs when your dog or cat bites and “eats” a flea. The intermediate form of the tapeworm is inside the flea’s body and it then attaches to the intestine and begins to grow “segments”. In about 3 weeks, these segments begin to pass in the stool. They are approximately ¼ to ½ inch long, flat, and white. After a short time in the air, they dry up to resemble a small yellow flat seed.  Diagnosis is made from seeing these segments on the stool or on the pet’s back end rather than a microscopic fecal exam. Treatment is either by oral tablets or by an injection. The tapeworm infection kills existing tapeworms but it does not prevent future infection. The only prevention is strict flea control. There is no direct transmission from dog or cat to a human.



This parasite is not a worm. It is a very tiny single-celled parasite that can live in the intestines of dogs, cats, and man.  It is most commonly seen in dogs coming out of kennel-type situations (pet stores, shelters, dog pounds, etc.) but its incidence is increasing. Symptoms include intermittent or continuous diarrhea, weight loss, depression, and loss of appetite. Diagnosis is made from a very fresh fecal specimen that must be collected at the clinic for optimum results. A surprising number of affected animals are “occult”; that is, they are infected but are negative on these tests even with multiple examinations. As a result, this parasite is often treated without a confirming diagnosis. Treatment is an oral medication administered at home. Prevention involves careful disposal of all fecal material and cleaning contaminated areas. Humans can become infected with Giardia so special care must be taken to wash hands and utensils.

There is a new Giardia vaccine available now as well.



This is also a single-celled parasite. It is seen primarily in puppies and kittens, although debilitated adults can also be affected. Transmission occurs by eating the infective stage of the parasite. It then reproduces in the intestinal tract causing no symptoms in mild cases to bloody diarrhea in severely affected pets. Diagnosis is made from a fresh stool sample. Treatment varies greatly. Animals showing no signs of illness are often not treated because a mild case is often self-limiting. Pets with diarrhea are treated at home with an oral medication. Severely affected pets may need hospitalization. Prevention involves disposal of all stools and cleaning the pet’s living area. Human transmission is uncommon but can occur.


If your pet has been diagnosed with one or more of the intestinal parasites listed above,

please follow the safety precautions listed below.


1.  Pick up your pet’s bowel movement and dispose of them.

2.  Bathe your pet once a week while they are being treated, this may help prevent re-infection from grooming.

3.  Do not let your pet lick you or your children, especially in the face.

4.  Wash your hands after playing with your pet.

5.   Give your pet’s worming medication as indicated by your veterinarian.

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